Paper window shade capable of transmitting light uniformly



Patented Apr. 25, 1939 PATENT OFFICE PAPER WINDOW SHADE CAPABLE OF TRANSMITTING IiIGHT UNIFORMLY Cornelius Anthony Alt, Newburgh, N. Y., assignon to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 11, 1936, Serial No. 110,298

'4 Claims.

This invention relates to paper window shades and the like. More particularly it relates to the preparation of translucent coated paper which transmits light uniformly and which does not 5 present a mottled appearance when viewed by transmitted light.

Window shades comprising a woven fabric coated with starch, drying oil or cellulose derivative compositions have been known for many 10 years. Within recent years a demand for window shades having a paper base has arisen. v The fact that paper window shades may be produced in a wider variety of designs and color combinations and at a lower cost than fabric window shades,

has, in a large measure, been responsible for this demand. Heretofore a satisfactory paper window shade has not been produced. Paper window shades have in the past (in line with the practice used for the preparation of fabric (textile) base window shades) been prepared by applying a coating composition to the smooth surfaced paper base and thereafter finishing the shade by embossing (usually to simulate a woven fabric).

When such sheet material is viewed by transmitted light, the embossed design or pattern is not distinctly visible as a uniform pattern throughout the area being viewed, and the sheet as a whole presents a mottled appearance. In addition, such shades do not transmit light uniformly.

As a result of these deficiencies, the paper shades made heretofore do not possess a desirable eye value. The expression "eye value is used in the art to describe the effect which the properties of a window shade have on an observer. Such features as translucency, uniformity of light transmittal, clearness and related features which contribute to the general appearance of the shade are responsible for this effect.

This invention had as an object the preparation of a paper window shade which did not present a mottled appearance when viewed by transmitted light. Other objects were the preparation of a paper window shade having the property of uniformly transmitting light and possessing a desirable eye value. Still further objects were the provision of a method for producing translucent, waterproof and readily cleanable coated paper base window shade material which gives the appearance of a coated woven fabric when viewed by transmitted light, and the preparation of paper window shade material of smooth feel and great durability. A general advance in the art and other objects which will appear hereinafter are also contemplated.

The foregoing objects and. related are accomplished in the manner set out in the following description in which details of what is believed to be the best mode for carrying out the invention are disclosed.

It has now been discovered that the aforementioned objects may be attained by subjecting a fibrous structure base material to an embossing operation which imparts thereto a pattern simulating that of a woven fabric, and thereafter coating the embossed base material with a protective 10 and/or decorative coating composition.

Further explanation of the invention is given in the following detailed description and illustrative specific examples, in which the parts are given by weight. Throughout the examples the 15 proportions of the ingredients on a solids basis (i. e., in the absence of solvents and diluents) are indicated by enclosing the percent of each solid material in parentheses.

Example I Per cent Cellulose nitrate (30.8) 35 Dibutyl phthalate (23.0) Leaded zinc oxide (46.2)

to the extent of approximately 0.7 ounce per square yard of solids of the coating composition. The percents given in the above coating compo- 4o sition (being in parentheses) include only the socalled solids", i. e., the solvents and diluents (for example ethyl acetate and ethyl alcohol) utilized to obtain a coating composition of the desired viscosity were omitted. This coating was 45 applied in several coats, each coat being dried by passing through a suitable drying chamber before applying a subsequent coating. Similar results have been obtained by applying the same amount of material in one coating operation. 50 The resulting embossed paper base material with a white coating had a rather prominent design.

In order to facilitate cleaning of the window shadeafter it had been placed in use (become rolled) the grain or pattern was somewhat flattened by passing the material through smooth pressure rolls. Desirable window shade material A very satisfactory product was produced in the manner described in Example I by coating only one side of the paper base material.

Example In A light brown (translucent) paper window shade was produced in the manner described in Example I by coating the paper base material with the following composition:

Per cent Cellulose nitrate 15.1 (28.8) Dibutyl phthalate 12.5 (23.7) Bone black 0.7 1.3) Leaded zinc oxide 22.5 (42.8) Chrome yellow 0.9 1.7) Chrome orange 0.9 1.7) Ethyl acetate 19.0

Ethyl alcohol 28.4

' Example IV A satisfactory pale green product was produced by following the procedure set forth in Example I, employing the following coating composition:

Per cent Cellulose acetate 15.1 (28.8) Dibutyl tartrate--. 12.5 (23.7) Leaded zinc oxide 23.8 (45.2) Chrome yellow 0.2 .4) Chrome green 1.0 1.9) Acetone 47.4

Example V A window shade material of pongee color was obtained by following the procedure of Example I and using the following coating composition:

. Per cent Cellulose nitrate 18.5 (44.5) Castor oil 7.7 (18.5) Ethyl acetate 23.4 Ethyl alcohol 35.0 Leaded zinc oxide 14.1 (33.9) Bone black 0.6 1.4) Chrome yellow 0.4 1.0) Chrome orange 0.3 0.7)

Example VI By using the following coating composition,

Per cent Cellulose nitrate 12.6 (21.0) Blown cottonseed oil 15.8 (26.5) Ethyl acetate 16.0 Ethyl alcohol 23.9 Bone black 2.3 3.8) Leaded zinc oxide 25.1 (41.6) Chrome yellow 1.6 2.6) Chrome orange 2.7 4.5)

and following the procedure described in Example I, a russet colored window shade material was obtained.

In the above examples it will be noted the ingredients representing the non-volatile components vary over the following range: v

The paper base material should preferably have a somewhat rough surface and/or possess absorbent properties so as to faciltate bonding the coating or impregnating composition to the fibrous base structure. Heavily sized or filled papers are not preferred because the tensile strength of such material is not uniformly satisfactory and because the bond between coating and the base is reduced to an undesirable value by the sizing and filling material. By using appropriate coating compositions on a proper paper base material a certain degree of impregnation may be obtained with the result that the finished sheet material has increased tensile strength. The degree of impregnation in such a case can be increased by subjecting the base to a preliminary treatment with so-called penetrant materials. In such instances the compatibility of the penetrant material and the cellulose derivative coating composition must be taken into consideration. Such substances as castor oil, cotton seed oil, dibutyl phthalate, dibutyl tartrate, tricresyl phosphate, ethylene glycol monoethyl ether and the like, as well as combinations of the same, may be used advantageously with cellulose nitrate and cellulose acetate coating compositions. These substances may be applied to the paper in low concentration solutions (in such media as ethyl acetate, ethyl alcohol, acetone and the like). If desired small amounts of cellulose derivatives such as cellulose nitrate and cellulose acetate may be incorporated in the penetran treating solution.

With due regard to the objects (specific and general) of the invention, the general requirements of the paper base are that it should possess suitable translucency, possess some absorbent properties, have sufficient tensile strength for the use intended, and be of such thickness as not to require an excessive amount of coating composition for the production of a final product of the necessary or desired final thickness.

The amount of coating material may vary according to the desired needs. Products in which the coating contained solids as low as 0.2 and as high as 1.4 ounces per square yard have been found desirable for various uses. It is not intended to limit the amount of solids which may be applied as a coating by specifically mentioning this range. In general this matter is governed by such factors as the thickness of the paper base used and the thickness desired in the finished product. For most general purposes a finished product (coated on both sides) having a thickness within the range of approximately 0.005 inch to approximately 0.012 inch has been found to be satisfactory.

If desired, the paper base material may be embossed by passing through the conventional embossing presses instead of through embossing rolls. As will be apparent to those skilled in the art, various designs of embossing may be utilized.

The paper base may be colored (dyed or pigmented) either by adding the coloring matter to the beater or by surface coloring after the paper is formed, care being taken that the paper is not rendered opaque by the coloring matter.

In general, all acid, basic and direct dyes, mineral pigments, natural and synthetic organic pigments, sulfur colors and vat colors are suitable for coloring paper. Since light fastness is a desideratum in window shades, the selection of the particular coloring matter is largely influenced by its resistance to light. Prussian blue is widely used in this field because of its excellent light resistance. Ochres and chrome yellows are satisfactory yellow components. Direct yellows possessing excellent fastness to light may be employed satisfactorily. Sulfur black and carbon black are very efficient dulling agents. As a general rule basic colors possess inferior light fastness. For optimum transparency pigment colors should be avoided. Vat dyes and pigments are so extremely fast to light that it is frequently desirable to balance the matter of transparency against the selection of colors available in the pigment field to produce the desired paper base.

The coated product may contain colors in the coating first applied and in subsequent coatings. By way of obtaining further decoration these colors, as well as those used to dye the base, may be of contrasting character. Printing, stencilling and other means well known in the art of decorating flexible base materials may be utilized in the production of a product having the desired eye value. A very desirable product has been produced by printing a design on the coated paper base material so that the final product simulates a Venetian blind. The printed design in this case is in color contrasting with the base material.

Variations in the ingredients of the'coating compositions within the scope of this invention will be apparent to those skilled in the art. The choice of a suitable coating composition as well as the degree of pigmentation of the composition, is governed by the degree of translucency and other properties desired in the finished product. Such substances as casein, starch,'drying oils, natural resins, synthetic resins and the like may, where desired, be used as components of the coating composition. Appropriate modification and the amounts of the ingredients of the coating compositions to produce desired properties, will be readily apparent to those skilled in the art, and when desired, the importance of variation in coating composition formulae may be readily determined empirically.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. The process of preparing translucent window shades which comprises embossing a strong paper having a thickness of approximately 0.007 inch to simulate woven fabric and thereafter coating the embossed paper with a pigmented cellulose derivative coating composition.

2. A process of preparing window shades which comprises embossing a 50 pound alpha paper weighing approximately 2.8 ounces per square yard and being approximately 0.007 inch in thickness, to simulate a woven fabric, coating the embossed paper with a composition consisting of:

Per cent Cellulose nitrate; 30.8 Dibutyl phthalate 23.0 Leaded zinc oxide 46.2

and thereafter slightly flattening the grain of the coated, embossed paper.

3. In the process of preparing translucent window shades from paper which does not have a strong mottled appearance when held up to a source of light, the improvement which comprises embossing a strong paper having a thickness of 0.005 to 0.012 inch to simulate woven fabric and thereafter applying a pigmented cellulose derivative coating composition in amount such that the solids deposited are between 0.2 and 1.4 ounces per square yard.

4. A process of preparing window shade material which comprises embossing a strong paper having a thickness of approximately "0.007 inch to simulate a woven fabric, the pattern on the back of the paper being counter to and less pronounced than the pattern on the face, and

thereafter applying a pigmented coating comhis 

